Dual-fuel internal combustion engines and associated control systems are generally known. By way of example, the Edwards U.S. Pat. No. 7,093,588 discloses a dual-fuel engine that uses both a first fuel such as diesel fuel, and a second fuel such as natural gas or propane gas. Dual fuel engines that are configured to use diesel fuel are configured to run in a “diesel only mode” using only diesel fuel. Such dual-fuel engines therefore have relatively high compression ratios suitable for the efficient operation of the engines (typically 16:1 or greater). These engines are started in the diesel only mode, and are operated in the dual fuel mode when the engines reach normal operating temperatures. Catalytic and other exhaust after-treatment systems can be utilized to bring the emissions outputs of these engines within applicable regulatory standards.
There remains a continuing need for improved dual-fuel engines. In particular, there is a need for improved diesel-natural gas engines.